1. Field of the Invention
The present invention relates to an inkjet recording apparatus operable to record an image on a recording medium.
2. Discussion of Related Art
JP-2007-105994A discloses an inkjet recording apparatus in which ink is supplied from an ink tank to a recording head via an ink supply tube (see FIG. 1 of the Japanese Publication). In this inkjet recording apparatus, a quantitative pump is provided in a non-end portion of the ink supply tube, so that a predetermined amount of the ink can be forced to flow from the ink tank to the recording head, by activation of the quantitative pump. The quantitative pump is a plunger pump including a plunger which is introduced in a cylinder and which extends to a distal end portion of the cylinder. The predetermined amount of the ink is conveyed by rotation of the plunger about its axis, which is made by a drive unit such as a motor.
In the disclosed inkjet recording apparatus, the above-described plunger has an end portion that is exposed outside the cylinder. It is considered that a motor is connected to the exposed end portion of the plunger. It is further considered that there is a small clearance between an outer circumferential surface of the plunger and an inner circumferential surface of the cylinder, since the plunger has to be rotatable in the cylinder. Therefore, the clearance has to be sealed by a sealing member such as an O-ring, for avoiding leakage of the ink through the clearance. Due to rotation of the plunger, the sealing member is likely to be worn down, and the wear of the sealing member would problematically cause fragments of the worn sealing members, entrance of air through the sealed clearance and leakage of the ink through the sealed clearance.